1. Field of the Invention
The present invention relates to a power source unit for an automotive vehicle, which is capable of parallel supply of mutually distinct supply voltages of power to a plurality of loads. More specifically, the invention relates to a power source unit for an automotive vehicle, which rectifies a power source voltage supplied from an alternator and drives a plurality of mutually distinct kinds of loads including a stator motor, independently of each other.
2. Description of the Related Arts
Japanese Unexamined Patent Publication (Kokai) 1-308133 discloses a power source unit for an automotive vehicle which employs a plurality of power generators for a parallel supply of power source voltages for a plurality of mutually distinct vehicular loads.
However, since spaces within engine rooms of automotive vehicles are strictly limited and the generators are generally driven by an output torque of engines via belts, orientations for installing the generators are quite limited, and therefore, only a few types of vehicles, which can provide sufficient space in the engine rooms, can employ a plurality of generators.
In general, the conventional power source unit of the automotive vehicle generates a source voltage by means of a three-phase alternator, and rectifies the source voltage by means of a three-phase full-wave rectifier for charging a single battery. The battery voltage is used for driving a start-up load system, such as a starter motor, and other non-start up load systems, in parallel.
On the other hand, Japanese Unexamined Patent Publication (Kokai) 60-102825 discloses a two voltage outputs type power source unit for an automotive vehicle, in which two batteries are connected in series, connected to both ends of a three-phase full-wave rectifier. In addition, a junction between two batteries and a neutral point of the three-phase full-wave rectifier is connected via a three-phase silicon controller rectifier bridge.
However, the electric load for an automotive vehicle is growing due to an installation of car telephone and so forth, and the above-mentioned type of power source unit, which has a pair of three-phase alternators and a single battery and will be hereafter referred to as "single battery type power source unit", may be subject to a problem of a drawing of a battery during an inoperative state of the engine, due to a large power consumption. Such a weak battery can affect the start-up characteristics of the engine.
Of course, such a problem may be resolved by providing a vehicular power source unit which has a pair of three-phase alternators and a battery for a load which is associated with a vehicular engine driving system including a starter or starter motor, which load will be hereafter referred to as "engine drive associated load", and another vehicular power source unit which also has another pair of three-phase alternators and a battery for a load which is irrelevant to the engine driving, and thus will be hereafter referred to as "non-engine drive associated load". However, such arrangement becomes too bulky.
In addition, where one of the outputs of the two voltage outputs type vehicular power source unit is connected to the engine start-up system, all loads utilizing the same voltage level to the engine start-up system must be connected to the engine start-up system channel. Therefore, a load on the battery for an engine drive associated load cannot be effectively reduced. Furthermore, in order to charge batteries connected in series, the three-phase alternator to be employed in the vehicular power source unit must be designed for a high voltage.